Moldings made from plastic with integrated electrically conducting layers or tracks are well-known, for example from the electrical and electronics industries.
Complicated cable harnesses have often been utilized hitherto for supply of electricity to components which bear electrical assemblies and which are used in the motor vehicle sector or in household machines, for example.
Another method attaches conductor tracks to the plastics surface by hot stamping. In this process, metal foils, for example composed of copper, gold, or nickel, with thicknesses which are generally from 18 to 150 μm, are stamped onto the plastics substrate, using a heated block.
Another group of processes involves the use of metallizable plastics which are arranged in multistage processes in such a way as to give conductor tracks via partial metallization.
The processes known hitherto for producing moldings from plastic with integrated conductor tracks are very costly and require complicated apparatus, and for this reason attempts are being made to find alternative options.
It is well known that plastics can be rendered electrically conductive via addition of electrically conductive particles. The extent of electrical conductivity can be influenced via the nature of the fillers, and their size, shape, distribution, and amount.
It is also known that the dependency of the electrical conductivity of a plastic on the amount of the particles used takes the form of what is known as a percolation curve. Accordingly, the plastic behaves as an electrical insulator at low filler contents. Starting at a certain amount of filler, the electrical conductivity suddenly rises, because bridges of conductive material form within the molding.
The production of plastics foams with foamed core and with solid outer skin is likewise known. Foams of this type are termed integral foams or structural foams (cf. Römpp, Lexikon Chemie, Stichwort “Schaumkunststoffe” [Römpp, Chemical Encyclopedia, keyword “plastics foams”], p. 3952, G. Thieme Verlag, Stuttgart, N.Y., 1997). These foams feature a highly non-uniform distribution of properties, such as density, within the structure (cf. J. L. Throne in Journal of Cellular Plastics, July/August 1972, p. 208–210, and Encyclopedia of Polymer Science and Engineering, Vol. 15, “Structural Foams”, p. 771–773, John Wiley & Sons, 1985).